Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
  • B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
  • B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
  • B32B17/10005—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing
  • B32B17/1055—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the resin layer, i.e. interlayer
  • B32B17/10761—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the resin layer, i.e. interlayer containing vinyl acetal
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F8/00—Chemical modification by after-treatment
  • C08F8/12—Hydrolysis
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F8/00—Chemical modification by after-treatment
  • C08F8/48—Isomerisation; Cyclisation

Definitions

• Vinyl acetate monomer is the primary raw material used in the manufacture of polyvinyl alcohol.
• Polyvinyl alcohol may be manufactured by polymerization of the vinyl acetate monomer to form polyvinyl acetate which is then partially hydrolyzed. The process of hydrolysis is based on the partial replacement of ester groups in the polyvinyl acetate with hydroxyl groups and may be completed in the presence of aqueous sodium hydroxide. Following gradual addition of a saponification agent, the polyvinyl alcohol may be precipitated, washed and dried. The degree of hydrolysis is determined by the time point at which the saponification reaction is terminated.
• the vinyl acetate monomer is available in a variety of different grades which in turn may be used to manufacture multiple grades of polyvinyl alcohol. In fact, depending upon the intended application of the polyvinyl alcohol product, one grade may actually be more advantageously used than another.
• polyvinyl acetate raw material is as a composite interlayer for laminated glass as generally described in U.S. Patent No. 6921509 to Moran et ah, the disclosure of which is incorporated by reference.
• Moran composite interlayers suitable for use in laminated glass include a layer of plasticized polyvinyl butyral, sandwiched between second and third polymeric layers.
• at least one and preferably both of the second and third layers are less than 5 mils thick and formed of polyurethane.
• U.S. Patent No. 7452608 to Fukatani et al. discloses a laminated glass and an intermediate film for laminated glass which is characterized as having high performance for mitigating external impact when, for instance, a head comes into collision due to the occurrence of a personal accident.
• the interlayer film for the laminated glass is not particularly limited but it is provided with a plasticizer in an amount of about 30 parts by weight or more, per 100 parts by weight of polyvinyl acetal resin interlayer.
• Disclosed herein is a process for manufacturing polyvinyl alcohol having an APHA color of less than or equal to about 10 for color sensitive applications, by feeding a purified vinyl acetate composition containing ultra-low levels of inhibitor to the polyvinyl acetate polymerization reactor.
• the purification of the vinyl acetate was made by using two distillation columns that remove the impurities, by products, and, in particular, all or substantially all remaining inhibitor from the vinyl acetate just prior to polymerization.
• the level of inhibitor is reduced to about 10 ppm or less, preferably about 5 ppm or less, even more preferably about 3 ppm or less, such as about 1 ppm or less.
• raw materials used in the manufacture of polyvinyl alcohol may be significant sources of color formation in the polyvinyl alcohol product.
• inhibitors and other heavy-end by-products from the vinyl acetate raw material stream may contribute to color formation in a polyvinyl alcohol product.
• Polyvinyl alcohol product made according to the present invention typically may be characterized as having an APHA color of less than or equal to about 10.
• Polyvinyl alcohol produced by conventional means typically may have an average APHA color of about 20 to 25. The lower the APHA color value, the more colorless the polyvinyl alcohol.
• the procedure for determining the APHA color number is set forth in ASTM D1209-62T and E202-62T. This method considers the intensity of the light and measures absorption in the yellow region of the visible spectra.
• APHA color is calibrated against distilled water, which is assigned an APHA value of zero and differing dilutions of platinum-cobalt (Pt Co), stock solution.
• Pt Co solutions are yellow as were the waste water solutions which APHA was originally designed to evaluate.
• low color values means polymers having stable APHA colors of less than or equal to about 10. Measurement of the APHA color of the polyvinyl alcohol is conducted on a 4 % solution of polyvinyl alcohol in water.
• APHA color is also to be considered in the measurement of APHA color.
• the length of the cuvette (10, 20 or 50 mm).
• Other color tests are available and may be conducted based on testing of solid polyvinyl polymers instead of polyvinyl alcohol in solution, and based against a standard yellowness index.
• Vinyl acetate is historically shipped in liquid form and with an inhibitor, such as hydroquinone or one or more quinine-based inhibitors.
• an inhibitor such as hydroquinone or one or more quinine-based inhibitors.
• impurities include inhibitors, heavy ends, resins, and alcohol by products.
• the quality of polyvinyl alcohol products useful for a wide variety of applications is significantly dependent on the color of the polyvinyl alcohol used to make the products.
• the color of the polyvinyl alcohol is significantly dependent on the color of the vinyl acetate monomer that may be polymerized to make polyvinyl acetate which is then hydrolyzed to make the polyvinyl alcohol product.
• impurities typically found in vinyl acetate monomers used as raw materials in the manufacture of polyvinyl alcohol in addition to hydroquinone are ethyl acetate, methyl acetate, acetone, acetaldehyde, crotonaldehyde, benzene and even water.
• Acetone is not believed to be an impurity that may cause color or other problems in polyvinyl alcohol products.
• Ethyl acetate is essentially a "pass through" in the polyvinyl alcohol process. It is essentially inert in the polymerization of the vinyl acetate monomer. Most of the ethyl acetate entering the paste stripper is sent overhead and accumulates in the recycle vinyl acetate monomer. At some point, it will move through the paste stripper and react with phosphoric acid added to the column to be converted to ethanol. This ethanol exits the base of the column and passes through the saponification step and acetic acid recovery system. In most or all conventional processes, it then reacts with the polyvinyl acetate polymer in the saponification step (as does methanol), to form ethyl acetate again. Any ethyl acetate from the saponification will pass into the acetic acid recovery system. Ethyl acetate entering the acetic acid recovery system is converted to ethanol and ultimately builds up in the methanol solvent, recycled in the process.
• Methyl acetate present in the vinyl acetate monomer converted to polyvinyl alcohol is of little or no concern because methyl acetate is a byproduct which manufacturers conventionally allow to be recycled with the recycled methanol in the manufacturing process to save energy costs.
• Acetaldehyde another so-called impurity contained in vinyl acetate monomer, is known to be a color promoting impurity in the final polyvinyl alcohol product. It is known however, that acetaldehyde can be converted to crotonaldehyde and higher aldol condensation oligomers, which are known to be good chain transfer agents, limiting molecular weight which is desirable in special grades of polyvinyl alcohol requiring lower molecular weight.
• the water content in the vinyl acetate should be as close as possible to the solubility limits of vinyl acetate monomer so as not to affect the quality of the polyvinyl alcohol.
• the inhibitors are typically used to stabilize the vinyl acetate from degradation from the time it is manufactured until it is polymerized to form polyvinyl acetate.
• Hydroquinone is probably the dominant color causing inhibitor used to stabilize vinyl acetate, but other quinine-based materials are also used commercially, including hydroquinone monomethyl ether and benzoquinone.
• These inhibitors which are generally present during shipping and storage of the vinyl acetate, should be reduced to the lowest possible level, prior to polymerization of the vinyl acetate to form polyvinyl acetate to reduce the color of the final polyvinyl alcohol product to the lowest possible level.
• the impurities included acetic acid, coloration agents, water and or cations and anions.
• the acetic acid may be removed by azeotopic distillation.
• the low color polyvinyl alcohol of the present invention may be useful for numerous applications where low color is important.
• polyvinyl alcohol is a main material for manufacturing polyvinyl butyral which is used as an adhesive for making laminated glass for automotive windshields, storm windows and doors, and in ballistic windows.
• Low color polyvinyl alcohol is also used as polarized film in liquid crystal display window applications.
• High color in polyvinyl alcohol such as APHA color values in excess of about 10, will affect the color of polyvinyl butyral and products made from it.
• High polyvinyl alcohol color values will also lead to poor aesthetic appearance and weathering resistance in polyvinyl alcohol polarized film applications.
• This example is provided to illustrate how vinyl acetate may be purified to remove any inhibitors.
• low inhibitor levels in vinyl acetate monomer are essential for reduction of high color in polyvinyl alcohol such as APHA color values.
• the boiling points of vinyl acetate and water are 162 degrees and 212 degrees fahrenheit respectively.
• an azeotrope of vinyl acetate and water are formed, having a boiling point of 151 degrees fahrenheit.
• the vinyl recovery column is operated in the range of 2 psig and 185 degrees fahrenheit.
• the vinyl acetate water azeotrope is distilled overhead, condensed, and phase separated in the accumulator. Vinyl acetate is returned to the column as reflux.
• the water and low boiling impurities are removed through the aqueous phase in the overhead accumulator.
• the high boiling impurities are removed through the column residue.
• the purified vinyl acetate is vapor fed to the redistillation column from the bottom of the vinyl recovery column. The redistillation column ensures that no entrained liquid containing impurities or inhibitors go into the polymerization reaction.
• Example 2 A stream of clean, clear vinyl acetate paste was prepared using purified vinyl acetate monomer, wherein the composition was more than 85 % distilled, making the impurity content equal to or less than about 1 ppm. This vinyl acetate stream was used to prepare a control sample.
• This vinyl acetate stream was used to prepare a control sample.
• four different impurities Acetaldehyde (“AH”), Hydroquinone (“HQ”), Hydroquinone Acetate (“HQDA”), and other acetic acid heavies such as Triacetene (herein collectively "HE-acid”), were added to the clean, clear paste, to measure color of the finished product.
• AH Acetaldehyde
• HQ Hydroquinone Acetate
• HQDA Hydroquinone Acetate
• HE-acid Triacetene
• samples of polyvinyl alcohol made according to the present invention exhibited very favorable, low color properties in comparison to the control samples.

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• Chemical & Material Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Joining Of Glass To Other Materials (AREA)
• Polymerisation Methods In General (AREA)

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• 2008
  • 2008-12-19 WO PCT/US2008/013929 patent/WO2009142616A1/en not_active Ceased
  • 2008-12-19 EP EP08874424A patent/EP2222461A1/en not_active Withdrawn
  • 2008-12-19 JP JP2010539502A patent/JP2011508802A/ja not_active Withdrawn
  • 2008-12-19 US US12/317,114 patent/US20090163658A1/en not_active Abandoned
  • 2008-12-19 CN CN2008801221019A patent/CN101903171A/zh active Pending

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